In the commercial harvesting of trees from a forest it is common practice to cut down trees, and to remove the branches and upper portions thereof to leave rather large logs. Each such log must be removed from the cutting area in the forest to a loading area for shipment by truck, train or boat. The cutting area is likely to be heavily wooded and may also have a great deal of underbrush. It is common practice to grip one end of a log with a grapple mechanism carried on a truck, often known as a log skidder, and to pull a log from the cutting area to a loading area with one end dragging on the ground.
A problem previously encountered is that the grapple is suspended from a swivel mechanism and tends to swing freely when it is not loaded. This is dangerous to anyone nearby and sometimes causes damage to the tractor itself. Even when the grapple is loaded it, and the front end of the log carried thereby, may start swinging back and forth with resultant danger, and with undue stress placed on the grapple and the remainder of the log skidder.
Efforts previously have been made to prevent free swinging of the grapple. In U.S. Pat. No. 3,592,503 a viscous liquid damper is used to inhibit swinging. This, however, does not stop swinging, but only slows it. Efforts also have been made to snub grapples by tightening bolts manually in the mounting swivels. This is slow and sometimes dangerous.